Maybe this thread isn't the place to get into Domino Theory. But why not? It really was relevant to some of us 'of a certain age'.
I was in HS when Castro brought the Communist Party of Cuba to power and the previous corrupt regime fled the country. (
Wikipedia). Domino Theory, a belief that this overthrow could easily extend into Latin America alongside USSR's efforts elsewhere, became a mainstream belief.
But along with this realistic concern was US political tribalism, with many liberals tarred with a label of 'communist sympathizer'. Name calling very much like today's refrain that liberal education will make schoolkids go trans or gay. Basically, the culture wars of the 60's, a reversal of the universality that got us through WWII, began then.
I chose PolSci major when I entered college. Later after JFK's 'Ask what you can do for your country' and reading about SE Asia in
The Ugly American, I signed up for Peace Corps. Mostly just for the sense of adventure, doing something interesting in a developing country.
But between the time I applied, waiting many months for a reply, and my acceptance, VN blew up. It had been an area of minor concern, somewhat like Somalia today - who cares what they do over there? Then suddenly a thousand 'advisors' became 10,000 troops on the ground, then you know the rest.
To my surprise Peace Corps accepted me to a urban development program in Venezuela, which along with Colombia was widely seen as where Castro would move next. The cities were full of kids newly arrived from rural areas, and who had no future. Exactly the tinder that revolutionaries can most easily recruit. (Like today in the Middle East). We taught rudimentary automechanics to these kids to help them become apprentices to real mechanics, hopefully before they fathered another generation with no future. US State Department was using us to fight communism, on the ground.
I was continually asked there, how the US government can promote peace and respect for America through efforts like we were doing, while at the same time dropping more bombs than were used in WWII, on the Vietnamese. How is that going to earn respect?
Reflecting on that, I continued to ask that question after I got home.